1  // Copyright (c) 2009-2010 Satoshi Nakamoto
  2  // Copyright (c) 2009-2022 The Bitcoin Core developers
  3  // Distributed under the MIT software license, see the accompanying
  4  // file COPYING or http://www.opensource.org/licenses/mit-license.php.
  5  
  6  #include <node/miner.h>
  7  
  8  #include <chain.h>
  9  #include <chainparams.h>
 10  #include <coins.h>
 11  #include <common/args.h>
 12  #include <consensus/amount.h>
 13  #include <consensus/consensus.h>
 14  #include <consensus/merkle.h>
 15  #include <consensus/tx_verify.h>
 16  #include <consensus/validation.h>
 17  #include <deploymentstatus.h>
 18  #include <logging.h>
 19  #include <node/context.h>
 20  #include <node/kernel_notifications.h>
 21  #include <policy/feerate.h>
 22  #include <policy/policy.h>
 23  #include <pow.h>
 24  #include <primitives/transaction.h>
 25  #include <util/moneystr.h>
 26  #include <util/signalinterrupt.h>
 27  #include <util/time.h>
 28  #include <validation.h>
 29  
 30  #include <algorithm>
 31  #include <utility>
 32  #include <numeric>
 33  
 34  namespace node {
 35  
 36  int64_t GetMinimumTime(const CBlockIndex* pindexPrev, const int64_t difficulty_adjustment_interval)
 37  {
 38      int64_t min_time{pindexPrev->GetMedianTimePast() + 1};
 39      // Height of block to be mined.
 40      const int height{pindexPrev->nHeight + 1};
 41      // Account for BIP94 timewarp rule on all networks. This makes future
 42      // activation safer.
 43      if (height % difficulty_adjustment_interval == 0) {
 44          min_time = std::max<int64_t>(min_time, pindexPrev->GetBlockTime() - MAX_TIMEWARP);
 45      }
 46      return min_time;
 47  }
 48  
 49  int64_t UpdateTime(CBlockHeader* pblock, const Consensus::Params& consensusParams, const CBlockIndex* pindexPrev)
 50  {
 51      int64_t nOldTime = pblock->nTime;
 52      int64_t nNewTime{std::max<int64_t>(GetMinimumTime(pindexPrev, consensusParams.DifficultyAdjustmentInterval()),
 53                                         TicksSinceEpoch<std::chrono::seconds>(NodeClock::now()))};
 54  
 55      if (nOldTime < nNewTime) {
 56          pblock->nTime = nNewTime;
 57      }
 58  
 59      // Updating time can change work required on testnet:
 60      if (consensusParams.fPowAllowMinDifficultyBlocks) {
 61          pblock->nBits = GetNextWorkRequired(pindexPrev, pblock, consensusParams);
 62      }
 63  
 64      return nNewTime - nOldTime;
 65  }
 66  
 67  void RegenerateCommitments(CBlock& block, ChainstateManager& chainman)
 68  {
 69      CMutableTransaction tx{*block.vtx.at(0)};
 70      tx.vout.erase(tx.vout.begin() + GetWitnessCommitmentIndex(block));
 71      block.vtx.at(0) = MakeTransactionRef(tx);
 72  
 73      const CBlockIndex* prev_block = WITH_LOCK(::cs_main, return chainman.m_blockman.LookupBlockIndex(block.hashPrevBlock));
 74      chainman.GenerateCoinbaseCommitment(block, prev_block);
 75  
 76      block.hashMerkleRoot = BlockMerkleRoot(block);
 77  }
 78  
 79  static BlockAssembler::Options ClampOptions(BlockAssembler::Options options)
 80  {
 81      options.block_reserved_weight = std::clamp<size_t>(options.block_reserved_weight, MINIMUM_BLOCK_RESERVED_WEIGHT, MAX_BLOCK_WEIGHT);
 82      options.coinbase_output_max_additional_sigops = std::clamp<size_t>(options.coinbase_output_max_additional_sigops, 0, MAX_BLOCK_SIGOPS_COST);
 83      // Limit weight to between block_reserved_weight and MAX_BLOCK_WEIGHT for sanity:
 84      // block_reserved_weight can safely exceed -blockmaxweight, but the rest of the block template will be empty.
 85      options.nBlockMaxWeight = std::clamp<size_t>(options.nBlockMaxWeight, options.block_reserved_weight, MAX_BLOCK_WEIGHT);
 86      return options;
 87  }
 88  
 89  BlockAssembler::BlockAssembler(Chainstate& chainstate, const CTxMemPool* mempool, const Options& options)
 90      : chainparams{chainstate.m_chainman.GetParams()},
 91        m_mempool{options.use_mempool ? mempool : nullptr},
 92        m_chainstate{chainstate},
 93        m_options{ClampOptions(options)}
 94  {
 95  }
 96  
 97  void ApplyArgsManOptions(const ArgsManager& args, BlockAssembler::Options& options)
 98  {
 99      // Block resource limits
100      options.nBlockMaxWeight = args.GetIntArg("-blockmaxweight", options.nBlockMaxWeight);
101      if (const auto blockmintxfee{args.GetArg("-blockmintxfee")}) {
102          if (const auto parsed{ParseMoney(*blockmintxfee)}) options.blockMinFeeRate = CFeeRate{*parsed};
103      }
104      options.print_modified_fee = args.GetBoolArg("-printpriority", options.print_modified_fee);
105      options.block_reserved_weight = args.GetIntArg("-blockreservedweight", options.block_reserved_weight);
106  }
107  
108  void BlockAssembler::resetBlock()
109  {
110      // Reserve space for fixed-size block header, txs count, and coinbase tx.
111      nBlockWeight = m_options.block_reserved_weight;
112      nBlockSigOpsCost = m_options.coinbase_output_max_additional_sigops;
113  
114      // These counters do not include coinbase tx
115      nBlockTx = 0;
116      nFees = 0;
117  }
118  
119  std::unique_ptr<CBlockTemplate> BlockAssembler::CreateNewBlock()
120  {
121      const auto time_start{SteadyClock::now()};
122  
123      resetBlock();
124  
125      pblocktemplate.reset(new CBlockTemplate());
126      CBlock* const pblock = &pblocktemplate->block; // pointer for convenience
127  
128      // Add dummy coinbase tx as first transaction. It is skipped by the
129      // getblocktemplate RPC and mining interface consumers must not use it.
130      pblock->vtx.emplace_back();
131  
132      LOCK(::cs_main);
133      CBlockIndex* pindexPrev = m_chainstate.m_chain.Tip();
134      assert(pindexPrev != nullptr);
135      nHeight = pindexPrev->nHeight + 1;
136  
137      pblock->nVersion = m_chainstate.m_chainman.m_versionbitscache.ComputeBlockVersion(pindexPrev, chainparams.GetConsensus());
138      // -regtest only: allow overriding block.nVersion with
139      // -blockversion=N to test forking scenarios
140      if (chainparams.MineBlocksOnDemand()) {
141          pblock->nVersion = gArgs.GetIntArg("-blockversion", pblock->nVersion);
142      }
143  
144      pblock->nTime = TicksSinceEpoch<std::chrono::seconds>(NodeClock::now());
145      m_lock_time_cutoff = pindexPrev->GetMedianTimePast();
146  
147      if (m_mempool) {
148          LOCK(m_mempool->cs);
149          m_mempool->StartBlockBuilding();
150          addChunks();
151          m_mempool->StopBlockBuilding();
152      }
153  
154      const auto time_1{SteadyClock::now()};
155  
156      m_last_block_num_txs = nBlockTx;
157      m_last_block_weight = nBlockWeight;
158  
159      // Create coinbase transaction.
160      CMutableTransaction coinbaseTx;
161      coinbaseTx.vin.resize(1);
162      coinbaseTx.vin[0].prevout.SetNull();
163      coinbaseTx.vin[0].nSequence = CTxIn::MAX_SEQUENCE_NONFINAL; // Make sure timelock is enforced.
164      coinbaseTx.vout.resize(1);
165      coinbaseTx.vout[0].scriptPubKey = m_options.coinbase_output_script;
166      coinbaseTx.vout[0].nValue = nFees + GetBlockSubsidy(nHeight, chainparams.GetConsensus());
167      coinbaseTx.vin[0].scriptSig = CScript() << nHeight << OP_0;
168      Assert(nHeight > 0);
169      coinbaseTx.nLockTime = static_cast<uint32_t>(nHeight - 1);
170      pblock->vtx[0] = MakeTransactionRef(std::move(coinbaseTx));
171      pblocktemplate->vchCoinbaseCommitment = m_chainstate.m_chainman.GenerateCoinbaseCommitment(*pblock, pindexPrev);
172  
173      LogPrintf("CreateNewBlock(): block weight: %u txs: %u fees: %ld sigops %d\n", GetBlockWeight(*pblock), nBlockTx, nFees, nBlockSigOpsCost);
174  
175      // Fill in header
176      pblock->hashPrevBlock  = pindexPrev->GetBlockHash();
177      UpdateTime(pblock, chainparams.GetConsensus(), pindexPrev);
178      pblock->nBits          = GetNextWorkRequired(pindexPrev, pblock, chainparams.GetConsensus());
179      pblock->nNonce         = 0;
180  
181      if (m_options.test_block_validity) {
182          if (BlockValidationState state{TestBlockValidity(m_chainstate, *pblock, /*check_pow=*/false, /*check_merkle_root=*/false)}; !state.IsValid()) {
183              throw std::runtime_error(strprintf("TestBlockValidity failed: %s", state.ToString()));
184          }
185      }
186      const auto time_2{SteadyClock::now()};
187  
188      LogDebug(BCLog::BENCH, "CreateNewBlock() chunks: %.2fms, validity: %.2fms (total %.2fms)\n",
189               Ticks<MillisecondsDouble>(time_1 - time_start),
190               Ticks<MillisecondsDouble>(time_2 - time_1),
191               Ticks<MillisecondsDouble>(time_2 - time_start));
192  
193      return std::move(pblocktemplate);
194  }
195  
196  bool BlockAssembler::TestChunkBlockLimits(FeePerWeight chunk_feerate, int64_t chunk_sigops_cost) const
197  {
198      if (nBlockWeight + chunk_feerate.size >= m_options.nBlockMaxWeight) {
199          return false;
200      }
201      if (nBlockSigOpsCost + chunk_sigops_cost >= MAX_BLOCK_SIGOPS_COST) {
202          return false;
203      }
204      return true;
205  }
206  
207  // Perform transaction-level checks before adding to block:
208  // - transaction finality (locktime)
209  bool BlockAssembler::TestChunkTransactions(const std::vector<CTxMemPoolEntryRef>& txs) const
210  {
211      for (const auto tx : txs) {
212          if (!IsFinalTx(tx.get().GetTx(), nHeight, m_lock_time_cutoff)) {
213              return false;
214          }
215      }
216      return true;
217  }
218  
219  void BlockAssembler::AddToBlock(const CTxMemPoolEntry& entry)
220  {
221      pblocktemplate->block.vtx.emplace_back(entry.GetSharedTx());
222      pblocktemplate->vTxFees.push_back(entry.GetFee());
223      pblocktemplate->vTxSigOpsCost.push_back(entry.GetSigOpCost());
224      nBlockWeight += entry.GetTxWeight();
225      ++nBlockTx;
226      nBlockSigOpsCost += entry.GetSigOpCost();
227      nFees += entry.GetFee();
228  
229      if (m_options.print_modified_fee) {
230          LogPrintf("fee rate %s txid %s\n",
231                    CFeeRate(entry.GetModifiedFee(), entry.GetTxSize()).ToString(),
232                    entry.GetTx().GetHash().ToString());
233      }
234  }
235  
236  void BlockAssembler::addChunks()
237  {
238      // Limit the number of attempts to add transactions to the block when it is
239      // close to full; this is just a simple heuristic to finish quickly if the
240      // mempool has a lot of entries.
241      const int64_t MAX_CONSECUTIVE_FAILURES = 1000;
242      constexpr int32_t BLOCK_FULL_ENOUGH_WEIGHT_DELTA = 4000;
243      int64_t nConsecutiveFailed = 0;
244  
245      std::vector<CTxMemPoolEntry::CTxMemPoolEntryRef> selected_transactions;
246      selected_transactions.reserve(MAX_CLUSTER_COUNT_LIMIT);
247      FeePerWeight chunk_feerate;
248  
249      // This fills selected_transactions
250      chunk_feerate = m_mempool->GetBlockBuilderChunk(selected_transactions);
251      FeePerVSize chunk_feerate_vsize = ToFeePerVSize(chunk_feerate);
252  
253      while (selected_transactions.size() > 0) {
254          // Check to see if min fee rate is still respected.
255          if (chunk_feerate_vsize << m_options.blockMinFeeRate.GetFeePerVSize()) {
256              // Everything else we might consider has a lower feerate
257              return;
258          }
259  
260          int64_t chunk_sig_ops = 0;
261          for (const auto& tx : selected_transactions) {
262              chunk_sig_ops += tx.get().GetSigOpCost();
263          }
264  
265          // Check to see if this chunk will fit.
266          if (!TestChunkBlockLimits(chunk_feerate, chunk_sig_ops) || !TestChunkTransactions(selected_transactions)) {
267              // This chunk won't fit, so we skip it and will try the next best one.
268              m_mempool->SkipBuilderChunk();
269              ++nConsecutiveFailed;
270  
271              if (nConsecutiveFailed > MAX_CONSECUTIVE_FAILURES && nBlockWeight +
272                      BLOCK_FULL_ENOUGH_WEIGHT_DELTA > m_options.nBlockMaxWeight) {
273                  // Give up if we're close to full and haven't succeeded in a while
274                  return;
275              }
276          } else {
277              m_mempool->IncludeBuilderChunk();
278  
279              // This chunk will fit, so add it to the block.
280              nConsecutiveFailed = 0;
281              for (const auto& tx : selected_transactions) {
282                  AddToBlock(tx);
283              }
284              pblocktemplate->m_package_feerates.emplace_back(chunk_feerate_vsize);
285          }
286  
287          selected_transactions.clear();
288          chunk_feerate = m_mempool->GetBlockBuilderChunk(selected_transactions);
289          chunk_feerate_vsize = ToFeePerVSize(chunk_feerate);
290      }
291  }
292  
293  void AddMerkleRootAndCoinbase(CBlock& block, CTransactionRef coinbase, uint32_t version, uint32_t timestamp, uint32_t nonce)
294  {
295      if (block.vtx.size() == 0) {
296          block.vtx.emplace_back(coinbase);
297      } else {
298          block.vtx[0] = coinbase;
299      }
300      block.nVersion = version;
301      block.nTime = timestamp;
302      block.nNonce = nonce;
303      block.hashMerkleRoot = BlockMerkleRoot(block);
304  
305      // Reset cached checks
306      block.m_checked_witness_commitment = false;
307      block.m_checked_merkle_root = false;
308      block.fChecked = false;
309  }
310  
311  void InterruptWait(KernelNotifications& kernel_notifications, bool& interrupt_wait)
312  {
313      LOCK(kernel_notifications.m_tip_block_mutex);
314      interrupt_wait = true;
315      kernel_notifications.m_tip_block_cv.notify_all();
316  }
317  
318  std::unique_ptr<CBlockTemplate> WaitAndCreateNewBlock(ChainstateManager& chainman,
319                                                        KernelNotifications& kernel_notifications,
320                                                        CTxMemPool* mempool,
321                                                        const std::unique_ptr<CBlockTemplate>& block_template,
322                                                        const BlockWaitOptions& options,
323                                                        const BlockAssembler::Options& assemble_options,
324                                                        bool& interrupt_wait)
325  {
326      // Delay calculating the current template fees, just in case a new block
327      // comes in before the next tick.
328      CAmount current_fees = -1;
329  
330      // Alternate waiting for a new tip and checking if fees have risen.
331      // The latter check is expensive so we only run it once per second.
332      auto now{NodeClock::now()};
333      const auto deadline = now + options.timeout;
334      const MillisecondsDouble tick{1000};
335      const bool allow_min_difficulty{chainman.GetParams().GetConsensus().fPowAllowMinDifficultyBlocks};
336  
337      do {
338          bool tip_changed{false};
339          {
340              WAIT_LOCK(kernel_notifications.m_tip_block_mutex, lock);
341              // Note that wait_until() checks the predicate before waiting
342              kernel_notifications.m_tip_block_cv.wait_until(lock, std::min(now + tick, deadline), [&]() EXCLUSIVE_LOCKS_REQUIRED(kernel_notifications.m_tip_block_mutex) {
343                  AssertLockHeld(kernel_notifications.m_tip_block_mutex);
344                  const auto tip_block{kernel_notifications.TipBlock()};
345                  // We assume tip_block is set, because this is an instance
346                  // method on BlockTemplate and no template could have been
347                  // generated before a tip exists.
348                  tip_changed = Assume(tip_block) && tip_block != block_template->block.hashPrevBlock;
349                  return tip_changed || chainman.m_interrupt || interrupt_wait;
350              });
351              if (interrupt_wait) {
352                  interrupt_wait = false;
353                  return nullptr;
354              }
355          }
356  
357          if (chainman.m_interrupt) return nullptr;
358          // At this point the tip changed, a full tick went by or we reached
359          // the deadline.
360  
361          // Must release m_tip_block_mutex before locking cs_main, to avoid deadlocks.
362          LOCK(::cs_main);
363  
364          // On test networks return a minimum difficulty block after 20 minutes
365          if (!tip_changed && allow_min_difficulty) {
366              const NodeClock::time_point tip_time{std::chrono::seconds{chainman.ActiveChain().Tip()->GetBlockTime()}};
367              if (now > tip_time + 20min) {
368                  tip_changed = true;
369              }
370          }
371  
372          /**
373           * We determine if fees increased compared to the previous template by generating
374           * a fresh template. There may be more efficient ways to determine how much
375           * (approximate) fees for the next block increased, perhaps more so after
376           * Cluster Mempool.
377           *
378           * We'll also create a new template if the tip changed during this iteration.
379           */
380          if (options.fee_threshold < MAX_MONEY || tip_changed) {
381              auto new_tmpl{BlockAssembler{
382                  chainman.ActiveChainstate(),
383                  mempool,
384                  assemble_options}
385                                .CreateNewBlock()};
386  
387              // If the tip changed, return the new template regardless of its fees.
388              if (tip_changed) return new_tmpl;
389  
390              // Calculate the original template total fees if we haven't already
391              if (current_fees == -1) {
392                  current_fees = std::accumulate(block_template->vTxFees.begin(), block_template->vTxFees.end(), CAmount{0});
393              }
394  
395              // Check if fees increased enough to return the new template
396              const CAmount new_fees = std::accumulate(new_tmpl->vTxFees.begin(), new_tmpl->vTxFees.end(), CAmount{0});
397              Assume(options.fee_threshold != MAX_MONEY);
398              if (new_fees >= current_fees + options.fee_threshold) return new_tmpl;
399          }
400  
401          now = NodeClock::now();
402      } while (now < deadline);
403  
404      return nullptr;
405  }
406  
407  std::optional<BlockRef> GetTip(ChainstateManager& chainman)
408  {
409      LOCK(::cs_main);
410      CBlockIndex* tip{chainman.ActiveChain().Tip()};
411      if (!tip) return {};
412      return BlockRef{tip->GetBlockHash(), tip->nHeight};
413  }
414  
415  std::optional<BlockRef> WaitTipChanged(ChainstateManager& chainman, KernelNotifications& kernel_notifications, const uint256& current_tip, MillisecondsDouble& timeout)
416  {
417      Assume(timeout >= 0ms); // No internal callers should use a negative timeout
418      if (timeout < 0ms) timeout = 0ms;
419      if (timeout > std::chrono::years{100}) timeout = std::chrono::years{100}; // Upper bound to avoid UB in std::chrono
420      auto deadline{std::chrono::steady_clock::now() + timeout};
421      {
422          WAIT_LOCK(kernel_notifications.m_tip_block_mutex, lock);
423          // For callers convenience, wait longer than the provided timeout
424          // during startup for the tip to be non-null. That way this function
425          // always returns valid tip information when possible and only
426          // returns null when shutting down, not when timing out.
427          kernel_notifications.m_tip_block_cv.wait(lock, [&]() EXCLUSIVE_LOCKS_REQUIRED(kernel_notifications.m_tip_block_mutex) {
428              return kernel_notifications.TipBlock() || chainman.m_interrupt;
429          });
430          if (chainman.m_interrupt) return {};
431          // At this point TipBlock is set, so continue to wait until it is
432          // different then `current_tip` provided by caller.
433          kernel_notifications.m_tip_block_cv.wait_until(lock, deadline, [&]() EXCLUSIVE_LOCKS_REQUIRED(kernel_notifications.m_tip_block_mutex) {
434              return Assume(kernel_notifications.TipBlock()) != current_tip || chainman.m_interrupt;
435          });
436      }
437      if (chainman.m_interrupt) return {};
438  
439      // Must release m_tip_block_mutex before getTip() locks cs_main, to
440      // avoid deadlocks.
441      return GetTip(chainman);
442  }
443  } // namespace node